Minimal implementation of fixed-length lists to enable wit-bindgen runtime tests

crates/cli-flags/src/lib.rs

@@ -409,6 +409,9 @@ wasmtime_option_group! {
         pub exceptions: Option<bool>,
         /// Whether or not any GC infrastructure in Wasmtime is enabled or not.
         pub gc_support: Option<bool>,
+        /// Component model support for fixed size lists: this corresponds
+        /// to the 🔧 emoji in the component model specification
+        pub component_model_fixed_size_list: Option<bool>,
     }
 
     enum Wasm {
@@ -1067,6 +1070,7 @@ impl CommonOptions {
             ("component-model-async", component_model_async_stackful, wasm_component_model_async_stackful)
             ("component-model-async", component_model_threading, wasm_component_model_threading)
             ("component-model", component_model_error_context, wasm_component_model_error_context)
+            ("component-model", component_model_fixed_size_list, wasm_component_model_fixed_size_lists)
             ("threads", threads, wasm_threads)
             ("gc", gc, wasm_gc)
             ("gc", reference_types, wasm_reference_types)

crates/environ/src/component/types.rs

@@ -89,6 +89,8 @@ indices! {
     pub struct TypeResultIndex(u32);
     /// Index pointing to a list type in the component model.
     pub struct TypeListIndex(u32);
+    /// Index pointing to a fixed size list type in the component model.
+    pub struct TypeFixedSizeListIndex(u32);
     /// Index pointing to a future type in the component model.
     pub struct TypeFutureIndex(u32);
 
@@ -296,6 +298,7 @@ pub struct ComponentTypes {
     pub(super) stream_tables: PrimaryMap<TypeStreamTableIndex, TypeStreamTable>,
     pub(super) error_context_tables:
         PrimaryMap<TypeComponentLocalErrorContextTableIndex, TypeErrorContextTable>,
+    pub(super) fixed_size_lists: PrimaryMap<TypeFixedSizeListIndex, TypeFixedSizeList>,
 }
 
 impl TypeTrace for ComponentTypes {
@@ -369,6 +372,7 @@ impl ComponentTypes {
             InterfaceType::Enum(i) => &self[*i].abi,
             InterfaceType::Option(i) => &self[*i].abi,
             InterfaceType::Result(i) => &self[*i].abi,
+            InterfaceType::FixedSizeList(i) => &self[*i].abi,
         }
     }
 
@@ -418,6 +422,7 @@ impl_index! {
     impl Index<TypeFutureTableIndex> for ComponentTypes { TypeFutureTable => future_tables }
     impl Index<TypeStreamTableIndex> for ComponentTypes { TypeStreamTable => stream_tables }
     impl Index<TypeComponentLocalErrorContextTableIndex> for ComponentTypes { TypeErrorContextTable => error_context_tables }
+    impl Index<TypeFixedSizeListIndex> for ComponentTypes { TypeFixedSizeList => fixed_size_lists }
 }
 
 // Additionally forward anything that can index `ModuleTypes` to `ModuleTypes`
@@ -595,6 +600,7 @@ pub enum InterfaceType {
     Future(TypeFutureTableIndex),
     Stream(TypeStreamTableIndex),
     ErrorContext(TypeComponentLocalErrorContextTableIndex),
+    FixedSizeList(TypeFixedSizeListIndex),
 }
 
 /// Bye information about a type in the canonical ABI, with metadata for both
@@ -1175,6 +1181,17 @@ pub struct TypeList {
     pub element: InterfaceType,
 }
 
+/// Shape of a "fixed size list" interface type.
+#[derive(Serialize, Deserialize, Clone, Hash, Eq, PartialEq, Debug)]
+pub struct TypeFixedSizeList {
+    /// The element type of the list.
+    pub element: InterfaceType,
+    /// The fixed length of the list.
+    pub size: u32,
+    /// Byte information about this type in the canonical ABI.
+    pub abi: CanonicalAbiInfo,
+}
+
 /// Maximum number of flat types, for either params or results.
 pub const MAX_FLAT_TYPES: usize = if MAX_FLAT_PARAMS > MAX_FLAT_RESULTS {
     MAX_FLAT_PARAMS

crates/environ/src/component/types_builder.rs

@@ -50,6 +50,7 @@ pub struct ComponentTypesBuilder {
     future_tables: HashMap<TypeFutureTable, TypeFutureTableIndex>,
     stream_tables: HashMap<TypeStreamTable, TypeStreamTableIndex>,
     error_context_tables: HashMap<TypeErrorContextTable, TypeComponentLocalErrorContextTableIndex>,
+    fixed_size_lists: HashMap<TypeFixedSizeList, TypeFixedSizeListIndex>,
 
     component_types: ComponentTypes,
     module_types: ModuleTypesBuilder,
@@ -118,6 +119,7 @@ impl ComponentTypesBuilder {
             type_info: TypeInformationCache::default(),
             resources: ResourcesBuilder::default(),
             abstract_resources: 0,
+            fixed_size_lists: HashMap::default(),
         }
     }
 
@@ -456,8 +458,8 @@ impl ComponentTypesBuilder {
             ComponentDefinedType::Stream(ty) => {
                 InterfaceType::Stream(self.stream_table_type(types, ty)?)
             }
-            ComponentDefinedType::FixedSizeList(..) => {
-                bail!("support not implemented for fixed-size-lists");
+            ComponentDefinedType::FixedSizeList(ty, size) => {
+                InterfaceType::FixedSizeList(self.fixed_size_list_type(types, ty, *size)?)
             }
             ComponentDefinedType::Map(..) => {
                 bail!("support not implemented for map type");
@@ -575,6 +577,33 @@ impl ComponentTypesBuilder {
         self.add_tuple_type(TypeTuple { types, abi })
     }
 
+    fn fixed_size_list_type(
+        &mut self,
+        types: TypesRef<'_>,
+        ty: &ComponentValType,
+        size: u32,
+    ) -> Result<TypeFixedSizeListIndex> {
+        assert_eq!(types.id(), self.module_types.validator_id());
+        let element = self.valtype(types, ty)?;
+        Ok(self.new_fixed_size_list_type(element, size))
+    }
+
+    pub(crate) fn new_fixed_size_list_type(
+        &mut self,
+        element: InterfaceType,
+        size: u32,
+    ) -> TypeFixedSizeListIndex {
+        let element_abi = self.component_types.canonical_abi(&element);
+        let mut abi = element_abi.clone();
+        // this assumes that size32 is already rounded up to alignment
+        abi.size32 = element_abi.size32 * size;
+        abi.size64 = element_abi.size64 * size;
+        abi.flat_count = element_abi
+            .flat_count
+            .map(|c| c.saturating_mul(size.min(255) as u8));
+        self.add_fixed_size_list_type(TypeFixedSizeList { element, size, abi })
+    }
+
     fn flags_type(&mut self, flags: &IndexSet<KebabString>) -> TypeFlagsIndex {
         let flags = TypeFlags {
             names: flags.iter().map(|s| s.to_string()).collect(),
@@ -691,6 +720,11 @@ impl ComponentTypesBuilder {
         intern_and_fill_flat_types!(self, tuples, ty)
     }
 
+    /// Interns a new tuple type within this type information.
+    pub fn add_fixed_size_list_type(&mut self, ty: TypeFixedSizeList) -> TypeFixedSizeListIndex {
+        intern_and_fill_flat_types!(self, fixed_size_lists, ty)
+    }
+
     /// Interns a new variant type within this type information.
     pub fn add_variant_type(&mut self, ty: TypeVariant) -> TypeVariantIndex {
         intern_and_fill_flat_types!(self, variants, ty)
@@ -826,6 +860,7 @@ impl ComponentTypesBuilder {
             InterfaceType::Enum(i) => &self.type_info.enums[*i],
             InterfaceType::Option(i) => &self.type_info.options[*i],
             InterfaceType::Result(i) => &self.type_info.results[*i],
+            InterfaceType::FixedSizeList(i) => &self.type_info.fixed_size_lists[*i],
         }
     }
 }
@@ -935,6 +970,7 @@ struct TypeInformationCache {
     options: PrimaryMap<TypeOptionIndex, TypeInformation>,
     results: PrimaryMap<TypeResultIndex, TypeInformation>,
     lists: PrimaryMap<TypeListIndex, TypeInformation>,
+    fixed_size_lists: PrimaryMap<TypeFixedSizeListIndex, TypeInformation>,
 }
 
 struct TypeInformation {
@@ -1084,6 +1120,24 @@ impl TypeInformation {
         self.build_record(ty.types.iter().map(|t| types.type_information(t)));
     }
 
+    fn fixed_size_lists(&mut self, types: &ComponentTypesBuilder, ty: &TypeFixedSizeList) {
+        let element_info = types.type_information(&ty.element);
+        self.depth = 1 + element_info.depth;
+        self.has_borrow = element_info.has_borrow;
+        match element_info.flat.as_flat_types() {
+            Some(types) => {
+                'outer: for _ in 0..ty.size {
+                    for (t32, t64) in types.memory32.iter().zip(types.memory64) {
+                        if !self.flat.push(*t32, *t64) {
+                            break 'outer;
+                        }
+                    }
+                }
+            }
+            None => self.flat.len = u8::try_from(MAX_FLAT_TYPES + 1).unwrap(),
+        }
+    }
+
     fn enums(&mut self, _types: &ComponentTypesBuilder, _ty: &TypeEnum) {
         self.depth = 1;
         self.flat.push(FlatType::I32, FlatType::I32);

crates/environ/src/fact/trampoline.rs

@@ -19,9 +19,10 @@ use crate::component::{
     CanonicalAbiInfo, ComponentTypesBuilder, FLAG_MAY_ENTER, FLAG_MAY_LEAVE, FixedEncoding as FE,
     FlatType, InterfaceType, MAX_FLAT_ASYNC_PARAMS, MAX_FLAT_PARAMS, PREPARE_ASYNC_NO_RESULT,
     PREPARE_ASYNC_WITH_RESULT, START_FLAG_ASYNC_CALLEE, StringEncoding, Transcode,
-    TypeComponentLocalErrorContextTableIndex, TypeEnumIndex, TypeFlagsIndex, TypeFutureTableIndex,
-    TypeListIndex, TypeOptionIndex, TypeRecordIndex, TypeResourceTableIndex, TypeResultIndex,
-    TypeStreamTableIndex, TypeTupleIndex, TypeVariantIndex, VariantInfo,
+    TypeComponentLocalErrorContextTableIndex, TypeEnumIndex, TypeFixedSizeListIndex,
+    TypeFlagsIndex, TypeFutureTableIndex, TypeListIndex, TypeOptionIndex, TypeRecordIndex,
+    TypeResourceTableIndex, TypeResultIndex, TypeStreamTableIndex, TypeTupleIndex,
+    TypeVariantIndex, VariantInfo,
 };
 use crate::fact::signature::Signature;
 use crate::fact::transcode::Transcoder;
@@ -1126,6 +1127,7 @@ impl<'a, 'b> Compiler<'a, 'b> {
             | InterfaceType::Future(_)
             | InterfaceType::Stream(_)
             | InterfaceType::ErrorContext(_) => 1,
+            InterfaceType::FixedSizeList(i) => self.types[*i].size as usize,
         };
 
         match self.fuel.checked_sub(cost) {
@@ -1165,6 +1167,9 @@ impl<'a, 'b> Compiler<'a, 'b> {
                     InterfaceType::ErrorContext(t) => {
                         self.translate_error_context(*t, src, dst_ty, dst)
                     }
+                    InterfaceType::FixedSizeList(t) => {
+                        self.translate_fixed_size_list(*t, src, dst_ty, dst);
+                    }
                 }
             }
 
@@ -2858,6 +2863,113 @@ impl<'a, 'b> Compiler<'a, 'b> {
         }
     }
 
+    fn translate_fixed_size_list(
+        &mut self,
+        src_ty: TypeFixedSizeListIndex,
+        src: &Source<'_>,
+        dst_ty: &InterfaceType,
+        dst: &Destination,
+    ) {
+        let src_ty = &self.types[src_ty];
+        let dst_ty = match dst_ty {
+            InterfaceType::FixedSizeList(t) => &self.types[*t],
+            _ => panic!("expected a fixed size list"),
+        };
+
+        // TODO: subtyping
+        assert_eq!(src_ty.size, dst_ty.size);
+
+        match (&src, &dst) {
+            // Generate custom code for memory to memory copy
+            (Source::Memory(src_mem), Destination::Memory(dst_mem)) => {
+                let src_mem_opts = match &src_mem.opts.data_model {
+                    DataModel::Gc {} => todo!("CM+GC"),
+                    DataModel::LinearMemory(opts) => opts,
+                };
+                let dst_mem_opts = match &dst_mem.opts.data_model {
+                    DataModel::Gc {} => todo!("CM+GC"),
+                    DataModel::LinearMemory(opts) => opts,
+                };
+                let src_element_bytes = self.types.size_align(src_mem_opts, &src_ty.element).0;
+                let dst_element_bytes = self.types.size_align(dst_mem_opts, &dst_ty.element).0;
+                assert_ne!(src_element_bytes, 0);
+                assert_ne!(dst_element_bytes, 0);
+
+                // because data is stored in-line, we assume that source and destination memory have been validated upstream
+
+                self.instruction(LocalGet(src_mem.addr.idx));
+                if src_mem.offset != 0 {
+                    self.ptr_uconst(src_mem_opts, src_mem.offset);
+                    self.ptr_add(src_mem_opts);
+                }
+                let cur_src_ptr = self.local_set_new_tmp(src_mem_opts.ptr());
+                self.instruction(LocalGet(dst_mem.addr.idx));
+                if dst_mem.offset != 0 {
+                    self.ptr_uconst(dst_mem_opts, dst_mem.offset);
+                    self.ptr_add(dst_mem_opts);
+                }
+                let cur_dst_ptr = self.local_set_new_tmp(dst_mem_opts.ptr());
+
+                self.instruction(I32Const(src_ty.size as i32));
+                let remaining = self.local_set_new_tmp(ValType::I32);
+
+                self.instruction(Loop(BlockType::Empty));
+
+                // Translate the next element in the list
+                let element_src = Source::Memory(Memory {
+                    opts: src_mem.opts,
+                    offset: 0,
+                    addr: TempLocal::new(cur_src_ptr.idx, cur_src_ptr.ty),
+                });
+                let element_dst = Destination::Memory(Memory {
+                    opts: dst_mem.opts,
+                    offset: 0,
+                    addr: TempLocal::new(cur_dst_ptr.idx, cur_dst_ptr.ty),
+                });
+                self.translate(&src_ty.element, &element_src, &dst_ty.element, &element_dst);
+
+                // Update the two loop pointers
+                self.instruction(LocalGet(cur_src_ptr.idx));
+                self.ptr_uconst(src_mem_opts, src_element_bytes);
+                self.ptr_add(src_mem_opts);
+                self.instruction(LocalSet(cur_src_ptr.idx));
+                self.instruction(LocalGet(cur_dst_ptr.idx));
+                self.ptr_uconst(dst_mem_opts, dst_element_bytes);
+                self.ptr_add(dst_mem_opts);
+                self.instruction(LocalSet(cur_dst_ptr.idx));
+
+                // Update the remaining count, falling through to break out if it's zero
+                // now.
+                self.instruction(LocalGet(remaining.idx));
+                self.ptr_iconst(src_mem_opts, -1);
+                self.ptr_add(src_mem_opts);
+                self.instruction(LocalTee(remaining.idx));
+                self.ptr_br_if(src_mem_opts, 0);
+                self.instruction(End); // end of loop
+
+                self.free_temp_local(cur_dst_ptr);
+                self.free_temp_local(cur_src_ptr);
+                self.free_temp_local(remaining);
+                return;
+            }
+            // for the non-memory-to-memory case fall back to using generic tuple translation
+            (_, _) => {
+                // Assumes that the number of elements are small enough for this unrolling
+                assert!(
+                    src_ty.size as usize <= MAX_FLAT_PARAMS
+                        && dst_ty.size as usize <= MAX_FLAT_PARAMS
+                );
+                let srcs =
+                    src.record_field_srcs(self.types, (0..src_ty.size).map(|_| src_ty.element));
+                let dsts =
+                    dst.record_field_dsts(self.types, (0..dst_ty.size).map(|_| dst_ty.element));
+                for (src, dst) in srcs.zip(dsts) {
+                    self.translate(&src_ty.element, &src, &dst_ty.element, &dst);
+                }
+            }
+        }
+    }
+
     fn translate_variant(
         &mut self,
         src_ty: TypeVariantIndex,

crates/wasmtime/src/config.rs

@@ -1296,6 +1296,16 @@ impl Config {
         self
     }
 
+    /// This corresponds to the 🔧 emoji in the component model specification.
+    ///
+    /// Please note that Wasmtime's support for this feature is _very_
+    /// incomplete.
+    #[cfg(feature = "component-model")]
+    pub fn wasm_component_model_fixed_size_lists(&mut self, enable: bool) -> &mut Self {
+        self.wasm_features(WasmFeatures::CM_FIXED_SIZE_LIST, enable);
+        self
+    }
+
     /// Configures whether the [Exception-handling proposal][proposal] is enabled or not.
     ///
     /// [proposal]: https://github.com/WebAssembly/exception-handling
@@ -2264,7 +2274,8 @@ impl Config {
             | WasmFeatures::CM_ASYNC_BUILTINS
             | WasmFeatures::CM_THREADING
             | WasmFeatures::CM_ERROR_CONTEXT
-            | WasmFeatures::CM_GC;
+            | WasmFeatures::CM_GC
+            | WasmFeatures::CM_FIXED_SIZE_LIST;
 
         #[allow(unused_mut, reason = "easier to avoid #[cfg]")]
         let mut unsupported = !features_known_to_wasmtime;

crates/wasmtime/src/runtime/component/func/typed.rs

@@ -2895,6 +2895,7 @@ pub fn desc(ty: &InterfaceType) -> &'static str {
         InterfaceType::Future(_) => "future",
         InterfaceType::Stream(_) => "stream",
         InterfaceType::ErrorContext(_) => "error-context",
+        InterfaceType::FixedSizeList(_) => "list<_, N>",
     }
 }
 

crates/wasmtime/src/runtime/component/types.rs

@@ -158,6 +158,7 @@ impl TypeChecker<'_> {
             (InterfaceType::Stream(_), _) => false,
             (InterfaceType::ErrorContext(_), InterfaceType::ErrorContext(_)) => true,
             (InterfaceType::ErrorContext(_), _) => false,
+            (InterfaceType::FixedSizeList(_), _) => todo!(), // FIXME(#12279)
         }
     }
 
@@ -855,6 +856,7 @@ impl Type {
             InterfaceType::Future(index) => Type::Future(instance.future_type(*index)),
             InterfaceType::Stream(index) => Type::Stream(instance.stream_type(*index)),
             InterfaceType::ErrorContext(_) => Type::ErrorContext,
+            InterfaceType::FixedSizeList(_) => todo!(), // FIXME(#12279)
         }
     }